Karina Keyla Tondato

Organization patterns of headwater-stream fish communities in the Upper Paraguay–Paraná basins

We compared environmental influences on the assemblages of stream fishes of contiguous but biogeographically distinct parts of the Upper Paraguay and Paraná basins in Brazil, aiming to describe the main distribution patterns of fish species in the headwater streams. We analyzed bimonthly samples in 10 streams in each basin from January to November 2004. Sixty fish species were collected, including 40 species in streams of the Paraguay Basin and 42 species in streams of the Paraná Basin. The species abundance rank did not differ between the basins. We found a clear differentiation between the Paraguay and Paraná stream fish assemblages. There were significant differences in species composition among streams, but no seasonal differences in species composition. Connectivity between streams explains the differences in species composition for the Paraguay streams, but not for the Paraná streams. Hydrological characteristics were the main factors determining species distribution in both basins, suggesting that the migratory capacity of each species and biogeographical barriers may act to filter the local species composition from the total species pool of colonizers.

Spatial and temporal distribution of fish larvae in marginal lagoons of Pantanal, Mato Grosso State, Brazil

An analysis was made of the spatial and temporal distribution of the abundance and composition of fish larvae assemblies, aiming to ascertain correlations with biotic and abiotic factors in marginal lagoons of the Cuiaba River floodplain in Brazils Pantanal wetlands. Samples were collected bimonthly in the pelagic region of the marginal lagoons (fourteen lagoons) close to the littoral zone covered by aquatic macrophytes from December 2006 to April 2007. The captured individuals consisted of 2,739 larvae, represented predominantly by Triportheus spp. (Characidae), Parodontidae, Anostomidae, Characidae and Serrasalmidae. Larval density varied among the sample lagoons in December, but the biotic (zooplankton density) and abiotic (water temperature, electrical conductivity, dissolved oxygen, pH, water transparency and lagoon depth) factors did not significantly affect larval composition and abundance. Larvae were captured throughout the sample period, with the highest densities occurring in December and early January. Temporally, lagoon depth, water transparency and fluviometric level showed a negative correlation with larval density. Both the zooplankton and the larval density vary positively, responding likewise to the environmental conditions imposed by flooding. The highest larval density was also found to coincide with the first rains (early December), when the rainfall has not yet reached its peak.

Assemblage of fish species associated with aquatic macrophytes in Porto Murtinho Pantanal, Mato Grosso do Sul, Brazil

The Porto Murtinho Pantanal lies at the limit of the Upper Paraguay River basin, and despite its biogeographical importance, several aspects of the ecology of the fish assemblage are not known. Monthly samples of fish associated with aquatic macrophytes were taken from February 2009 through January 2011. A total of 46,327 individuals were collected, belonging to 144 species. Characiformes and Siluriformes were the predominant orders, and Odontostilbe pequira, O. paraguayensis and Bryconamericus exodon were the most abundant species. Two species, Cynopotamus sp. and Pimelodus mysteriosus, were recorded for the first time in the Pantanal, and a new occurrence record of Cichla piquiti was observed, representing an approximately 400 km range expansion in your distribution area in the Pantanal.